//The MIT License

//Copyright (c) 2009 Lluis Sanchez, Nick Darnell

//Permission is hereby granted, free of charge, to any person obtaining a copy
//of this software and associated documentation files (the "Software"), to deal
//in the Software without restriction, including without limitation the rights
//to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//copies of the Software, and to permit persons to whom the Software is
//furnished to do so, subject to the following conditions:

//The above copyright notice and this permission notice shall be included in
//all copies or substantial portions of the Software.

//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//THE SOFTWARE.

using System;
using System.Reflection.Emit;

namespace Polymorph
{
    public class CodeIs : CodeConditionExpression
    {
        Type type;
        CodeExpression exp;

        public CodeIs(Type type, CodeExpression exp)
        {
            this.type = type;
            this.exp = exp;
        }

        public override void Generate(ILGenerator gen)
        {
            Type typeObj = exp.ResultType;

            if (type.IsAssignableFrom(typeObj))
            {
                gen.Emit(OpCodes.Ldc_I4_1);
                return;
            }
            else if (!typeObj.IsAssignableFrom(type))
            {
                gen.Emit(OpCodes.Ldc_I4_0);
                return;
            }

            exp.Generate(gen);
            gen.Emit(OpCodes.Isinst, type);
            gen.Emit(OpCodes.Ldnull);
            gen.Emit(OpCodes.Cgt_Un);
        }

        public override void GenerateForBranch(ILGenerator gen, Label label, bool branchCase)
        {
            Type typeObj = exp.ResultType;

            if (type.IsAssignableFrom(typeObj))
            {
                if (branchCase)
                    gen.Emit(OpCodes.Br, label);
                return;
            }
            else if (!typeObj.IsAssignableFrom(type))
            {
                if (!branchCase)
                    gen.Emit(OpCodes.Br, label);
                return;
            }

            exp.Generate(gen);
            gen.Emit(OpCodes.Isinst, type);
            if (branchCase)
                gen.Emit(OpCodes.Brtrue, label);
            else
                gen.Emit(OpCodes.Brfalse, label);
        }

        public override void PrintCode(CodeWriter cp)
        {
            exp.PrintCode(cp);
            cp.Write(" is ");
            cp.Write(type.FullName);
        }

        public override Type ResultType
        {
            get { return typeof(bool); }
        }
    }
}